How to merge FLV or MP4 (MPEG-4 AVC + AAC) files (or convert, then merge)

[cmdj1982]

Can anyone help me properly merge my mp4s? I've tried some "mp4 mergers" out there, but they all suck. All the generic video mergers don't work either. If anything has successfully merged my files, they all get more and more out of synch as the video progresses after each newly merged part starts playing.

I've been trying to make VirtualDub mp4 compatible and I've gotten to the point where I can open mp4s for editing through AVISynth Script, but I cannot append the segments like I want to addon the next files to the end of the first. If I must I suppose I can re-encode them to avi and merge them, but I'd really rather not. Any suggestions? I tried opening the mp4s in avidemux, but no dice. Unrecognizable format.

The mp4s are being recorded from a flash-embedded source and are saved as flvs are my HD, then I use FLVExtract to get them into h.264/aac mode and mux them together with Yamb to get the resulting mp4 specs (from GSpot):

Codec: avc1
Name: H.264/MPEG-4 AVC
Status: Codec Status Undetermined
kbps: 1138
fps: 29.971
Audio: mp4a1-MPEG-4 AAC LC
kbps: 47kb/s

These specs are universal for all my muxed mp4s, as well as the aspect ratio of 640x360. I've tried simply using Yamb to merge them, but the result is a full-size media file that pops out and plays all the video streams at once instead of sequentially. Very annoying and frustrating.


Fortunately I can play the files at this point on my WDTV player, which is the end-goal, but I really want them merged into one file for ease of file management and sharing.

Thanks a ton for any and all help! Again, my name problem with the merging is that the audio gets out of synch as the merged files progress (because of the way those generic programs merge files, it's not done very seamlessly). Just need one that will merge while keeping the audio in synch the whole time.